Crystallization and preliminary diffraction data of 60-kDa glycosylated pollen isoallergens from Bermuda grass

Crystals grown from a 60-kDa isoallergen mixture of Bermuda grass pollen have been obtained in 30% PEG 4000 and 25% isopropanol. The crystals diffract beyond 2-A resolution and belong to a tetragonal space group with the unit cell dimensions a = b = 86 A and c = 310 A. The preferential crystal growth of the larger isoallergens with a blocked N-terminus indicates that crystallization can isolate proteins with compact conformation.

HLA-C disparity between patients and unrelated donors matched for HLA-A, -B, and -DRB1 alleles: impact of serological vs. DNA typing for HLA-A and -B loci

High incidences of graft failure, graft-vs.-host disease (GVHD), and serious infections following unrelated donor (URD) marrow transplantation, despite apparent human leukocyte antigen (HLA) identity, may reflect the presence of molecular disparities, including those for HLA-C alleles between the patient and the URD. The level of these disparities could be significant, because as many as 42 alleles are currently known for HLA-C locus. We studied 84 patients and 251 potential URDs to evaluate 1) the extent of HLA-C disparity between the patient and the URD identified by serology for HLA-A and -B and by DNA typing for -DRB1 and 2) the level of HLA-C disparity between patients and URDs matched by high-resolution DNA typing for HLA-A, -B, and -DRB1. The DNA typing was performed at the Memorial Sloan Kettering Cancer Center, and the serotyping was provided by the registries. Of 251 URDs matched by HLA-A and -B serology and -DRB1 (sA_sB_dnaDRB1 ); 94, 75, and 82 were 6/6, 5/6, and 4/6 matches, respectively. Of 94 sA_sB_dnaDRB1 6/6 URDs, 51 (54.3%) were matched for both HLA-C alleles. In contrast, 31 (41.3%) 5/6 (p=0.12) and 15 (18.3%) 4/6 (p < 0.01) sA_sB_dnaDRB1 URDs were matched for both HLA-C alleles. Following DNA typing for HLA-A and -B, 52 (55.3%) of 94 6/6, 30 (40%) of 75 5/6, and 25 (30.5%) of 82 4/6 sA_sB_dnaDRB1 URDs remained 6/6, 5/6, and 4/6 matches at the DNA level (dnaA_B_DRB1). HLA-C disparities continued to exist in the dnaA_B_DRB1 URD group. Of 54 dnaA_B_DRB1 6/6 URDs, 41 (75.9%) were matched for both HLA-C alleles. Only 45.3% of the 5/6 (p=0.01) and 22.2% of the 4/6 (p < 0.01) dnaA_B_DRB1 URDs were matched for both HLA-C alleles. In the 6/6 category, the frequency of HLA-C matching improved (75.9 vs. 54.3%; p=0.01) following DNA matching for HLA-A and -B. In comparison to mismatching for HLA-B locus, mismatching for either HLA-DRB1 or -A resulted in a lower odds ratio for HLA-C disparity. The presence of a common haplotype in the sA_sB_dnaDRBl (p=0.06) URD category improved the level of HLA-C matching. We identified alleles that are associated with high (B*1501, B*4402, B*5101, DRB1*0101, A*0201, A*1101, A*2301, and A*3201) or low (B*0702, B*0801, B*1302, B*3502, DRB1*0301, DRB1*1104, A*0101, A*3001, and A*6801) probability of HLA-C disparity. Overall, sA_sB_dnaDRB1 as well as dnaA_B_DRB1 matched URDs for non-Caucasian patients were more likely to have HLA-C disparity in comparison to the matched URDs of Caucasian patients. However, a high incidence of HLA-C disparities was identified even in the URDs for Caucasian patients. Whether the disparities demonstrated by this study contribute to the higher immunological complications noted following URD bone marrow transplantation is unclear. Outcome analysis and studies aimed at understanding the functional role of HLA-C may provide an answer.

Human brain short chain L-3-hydroxyacyl coenzyme A dehydrogenase is a single-domain multifunctional enzyme. Characterization of a novel 17beta-hydroxysteroid dehydrogenase

Human brain short chain L-3-hydroxyacyl-CoA dehydrogenase (SCHAD) was found to catalyze the oxidation of 17beta-estradiol and dihydroandrosterone as well as alcohols. Mitochondria have been demonstrated to be the proper location of this NAD+-dependent dehydrogenase in cells, although its primary structure is identical to an amyloid beta-peptide binding protein reportedly associated with the endoplasmic reticulum (ERAB). This fatty acid beta-oxidation enzyme was identified as a novel 17beta-hydroxysteroid dehydrogenase responsible for the inactivation of sex steroid hormones. The catalytic rate constant of the purified enzyme was estimated to be 0.66 min-1 with apparent Km values of 43 and 50 microM for 17beta-estradiol and NAD+, respectively. The catalytic efficiency of this enzyme for the oxidation of 17beta-estradiol was comparable with that of peroxisomal 17beta-hydroxysteroid dehydrogenase type 4. As a result, the human SCHAD gene product, a single-domain multifunctional enzyme, appears to function in two different pathways of lipid metabolism. Because the catalytic functions of human brain short chain L-3-hydroxyacyl-CoA dehydrogenase could weaken the protective effects of estrogen and generate aldehydes in neurons, it is proposed that a high concentration of this enzyme in brain is a potential risk factor for Alzheimer's disease.

Cytochrome P450 1A1 genetic polymorphisms and risk of hepatocellular carcinoma among chronic hepatitis B carriers

Cigarette smoking has been associated with increased risk of hepatocellular carcinoma (HCC) in some epidemiological studies. Cytochrome P450 1A1 (CYP1A1) is involved in the biotransformation of tobacco-derived polycyclic aromatic hydrocarbons (PAHs) into carcinogenic metabolites. The aim of this study was to determine whether CYP1A1 polymorphisms were related to HCC risk among chronic hepatitis B virus (HBV) carriers. Genotypic variants of CYP1A1 were determined using polymerase chain reaction in 81 incident cases of HCC and 409 controls nested in a cohort study of 4841 male chronic HBV carriers. No overall association between CYP1A1 genotypes and HCC was observed. The presence of the Mspl (odds ratio (OR) 3.15, P = 0.0196) or Ile-Val (OR 1.99, P = 0.0855) variant allele of CYP1A1 increased HCC risk among smokers, but posed no increased risk among non-smokers. The smoking-related HCC risk was most pronounced among those who had a susceptible allele of the CYP1A1 and a deficient genotype of glutathione S-transferase M1, which detoxifies PAH electrophilic metabolites produced by CYP1A1. In the absence of the Ile-Val variant allele, the Mspl polymorphism was still associated with smoking-related HCC. This study suggests that tobacco-derived PAHs play a role in HCC risk among chronic HBV carriers, and CYP1A1 polymorphism is an important modulator of the hepatocarcinogenic effect of PAHs. The Mspl and Ile-Val polymorphisms of CYP1A1 may have different mechanisms for increasing susceptibility to smoking-related HCC.

Polarizing microscopy of eyespot of Chlamydomonas: in situ observation of its location, orientation, and multiplication

The eyespot in the cell of Chlamydomonas reinhardtii has been found to appear as a bright spot under the cross polar setting of a polarizing microscope. This was confirmed by isolating the eyespot from a homogenate of wall-deficient mutant cw-15, and by observing it under a polarizing microscope. Thus, the eyespot was proved to be a strongly birefringent body. Next, gametes (mt+ and mt-) of 137c strain were prepared by cultivating it in a low-nitrogen (NH4Cl) medium. Here, every cell shows only one (and never more than one) birefringent spot. The birefringent eyespot was located always near the surface on the "equator," that is, at the farthest point from the "meridionial" cell-axis that is defined as the bisector of the two flagella projected out from the cell surface. It was shown, in addition, that the optic axis of this birefringent eyespot is oriented in the cell always along the parallel direction of the cell axis defined above. Thus, the polarizing microscopy has been shown to provide a powerful method for in vivo, in situ pursuit of the eyespot of Chlamydomonas.

Expression of insulin growth factor-1 splice variants and structural genes in rabbit skeletal muscle induced by stretch and stimulation

1. Skeletal muscle is a major source of circulating insulin growth factor-1 (IGF-1), particularly during exercise. It expresses two main isoforms. One of the muscle IGF-1 isoforms (muscle L.IGF-1) is similar to the main liver IGF-1 and presumably has an endocrine action. The other muscle isoform as a result of alternative splicing has a different 3' exon sequence and is apparently designed for an autocrine/paracrine action (mechano-growth factor, MGF). Using RNase protection assays with a probe that distinguishes these differently spliced forms of IGF-1, their expression and also the expression of two structural genes was measured in rabbit extensor digitorum longus muscles subjected to different mechanical signals. 2. Within 4 days, stretch using plaster cast immobilization with the limb in the plantar flexed position resulted in marked upregulation of both forms of IGF-1 mRNA. Electrical stimulation at 10 Hz combined with stretch (overload) resulted in an even greater increase of both types of IGF-1 transcript, whereas electrical stimulation alone, i.e. without stretch, resulted in no significant increase over muscle from sham-operated controls. Previously, it was shown that stretch combined with electrical stimulation of the dorsiflexor muscles in the adult rabbit results in a marked increase in muscle mass involving increases in both length and girth, within a few days. The expression of both systemic and autocrine IGF-1 growth factors provides a link between the mechanical signal and the marked increase in the structural gene expression involved in tissue remodelling and repair. 3. The expression of the beta actin gene was seen to be markedly upregulated in the stretched and stretched/stimulated muscles. It was concluded that the increased expression of this cytoskeletal protein gene is an indication that the production of IGF-1 may initially be a response to local damage. 4. Switches in muscle fibre phenotype were studied using a specific gene probe for the 2X myosin heavy chain gene. Type 2X expression was found to decrease markedly with stimulation alone and when electrical stimulation was combined with stretch. Unlike the induction of IGF-1 and beta actin, the decreased expression of the 2X myosin mRNA was less marked in the 'stretch only' muscles. This indicates that the interconversion of fibre type 2X to 2A may in some situations be commensurate with, but not under the control of IGF-1.

A p53 genetic polymorphism as a modulator of hepatocellular carcinoma risk in relation to chronic liver disease, familial tendency, and cigarette smoking in hepatitis B carriers

This study evaluated whether the codon 72 p53 polymorphism was related to hepatocellular carcinoma (HCC). Genotypes of p53 were determined in 80 incident cases of HCC and 328 controls nested in a cohort study of 4,841 male chronic hepatitis B carriers. No overall increase in HCC risk with the Pro variant allele of the p53 polymorphism was apparent. However, there were synergistic effects on HCC development for the Pro allele with chronic liver disease and family history of HCC in first-degree relatives. Compared with subjects without the Pro allele and chronic liver disease, the increase in HCC risk associated with chronic liver disease among those without the Pro allele was only threefold. Subjects with both chronic liver disease and the Pro allele were at an increased risk of 7.60 (95% CI = 2.28-25.31). When subjects without family history of HCC and the Pro allele were considered as the reference group, there was no apparent increased risk of HCC for those without the Pro allele who had family history of HCC. Among those with both factors, there was a significantly increased risk of 3.29 (95% CI = 1.10-9.85). Both cigarette smoking and glutathione S-transferase M1 genotype modified the risk of HCC associated with the p53 polymorphism. Significantly increased risk associated with the p53 genotype was observed only among smokers who were glutathione S-transferase-null (Pro/Pro vs. Arg/Arg: odds ratio = 6.46; 95% CI = 1.55-26.94). The p53 polymorphism also interacted with the cytochrome P450 1A1 and carotenoid levels in smoking-related hepatocarcinogenesis.

Hormone-refractory prostate cancer cells express functional follicle-stimulating hormone receptor (FSHR)

PURPOSE

Understanding growth regulation in hormone-refractory prostate cancer may provide avenues for novel treatment interventions. This study was conducted to characterize the expression of the receptor (FSHR) for follicle-stimulating hormone (FSH) in androgen-independent prostate cancer cell lines and in human malignant prostate tissues.

MATERIALS AND METHODS

Western blotting, immunohistochemistry (IHC), and flow cytometric analysis were used to study the expression of FSHR. The effect of FSH on cell growth and clonogenicity was studied using proliferation and clonogenic assays.

RESULTS

Immunohistochemistry revealed expression of FSH in PC3 and Du145 cells. FSHR was identified in PC3 and Du145 cells, as well as in human adenocarcinoma of the prostate. The specificity of the FSHR detected on prostate cancer tissues or cells by IHC and Western blotting was confirmed by preabsorbing the antibodies with the immunizing antigens. Stimulation of these hormone-refractory cells with FSH triggered a proliferative response in vitro, suggesting that the receptor is biologically active.

CONCLUSION

Hormone-refractory prostate cancer cells express FSH and biologically active FSHR. Our results suggest that FSHR and its ligand may play a role in the regulation of the growth of hormone-refractory prostate cancers.

Identity of heart and liver L-3-hydroxyacyl coenzyme A dehydrogenase

Rat heart and liver cDNAs for precursor of L-3-hydroxyacyl-CoA dehydrogenase have been cloned and sequenced. The results indicate that these different rat organs express identical dehydrogenases. Furthermore, pig heart mRNA for L-3-hydroxyacyl-CoA dehydrogenase precursor was amplified by reverse transcription-polymerase chain reaction, and all the cDNA clones were found to encode a precursor of liver L-3-hydroxyacyl-CoA dehydrogenase (X.-Y. He, S.-Y. Yang, Biochim. Biophys. Acta 1392 (1998) 119-126) but not the well-documented heart form of the dehydrogenase (K.G. Bitar et al., FEBS Lett. 116 (1980) 196-198). Sequencing data and other evidence establish that the pig, like the rat, has the same dehydrogenase in heart and liver. Since the size and structure of pig heart L-3-hydroxyacyl-CoA dehydrogenase are identical to the pig liver dehydrogenase, reports that relied on the published sequence of the pig heart dehydrogenase need to be re-evaluated. For example, the signature pattern of the L-3-hydroxyacyl-CoA dehydrogenase family is HXFXPX3MXLXE. Furthermore, the published crystal structure of the pig heart dehydrogenase that substantiated each subunit comprising 307 residues with a mercury-binding residue at position 204 (J.J. Birktoft et al., Proc. Natl. Acad. Sci. U.S.A. 84 (1987) 8262-8266) must be re-examined in accordance with this revelation.

Clinical results of the transoral operation for lesions of the craniovertebral junction and its abnormalities

BACKGROUND

We treated 20 cases of craniovertebral junction lesions via a transoral approach. Developmental abnormalities of the craniovertebral junction accounted for 15 cases; there were 3 cases of tumor, 1 case of osteomyelitis, and 1 case of rheumatoid arthritis.

METHODS

The transoral transpharyngeal approach was used in all cases. In 17 non-tumoral patients the anterior margin of the atlas and the odontoid process were resected. In one patient with a ventral clivus chordoma, both a transoral and a transnasal transsphenoidal approach was used for partial resection of the tumor mass. In two cases the median transpharyngeal approach was combined with a jaw-facial incision. In one case a metastatic adenocarcinoma, and in another a neurinoma of the accessory nerve straddling the posterior fossa and the pharyngeal region were removed.

RESULTS

After operation four cases developed craniovertebral joint instability and required posterior cervical fusion or external fixation with a halo brace. Follow-up ranged from 2 to 44 months. In most patients neurologic function slowly improved. One worsened, and one died of respiratory failure after operation. Two patients with malignant tumors died during the follow-up period.

CONCLUSION

In patients with developmental malformations, transoral decompression will result in some neurologic improvement and arrest the progress of symptoms. Patients with tumors are likely to show a good neurologic outcome when transoral surgery is performed in the early stage of the condition.

Intracoronary propofol attenuates myocardial but not coronary endothelial dysfunction after brief ischaemia and reperfusion in dogs

We have investigated the effects of propofol on recovery of regional mechanical and coronary endothelial function and on lipid peroxidation in post-ischaemic myocardium in dogs. The animals were assessed for 180 min during reperfusion after 15-min of occlusion of the left anterior descending coronary artery (LAD). They were treated with intracoronary (i.c.) propofol 5 or 20 micrograms/ml of coronary flow or vehicle (control group) for 60 min, beginning 30 min before LAD occlusion. Propofol significantly enhanced recovery of regional contractile function (70% and 81% of baseline segment shortening in the propofol 5 and 20 micrograms ml-1 groups, respectively, compared with 51% in controls at 3 h of reperfusion). However, LAD flow responses to i.c. acetylcholine were similarly attenuated regardless of treatment with propofol throughout reperfusion. The increase in malondialdehyde induced by ischaemia-reperfusion was significantly suppressed by both doses of propofol. These results demonstrated that in vivo, propofol ameliorated dysfunction of the myocardium but not of the coronary endothelium resulting from brief ischaemia and reperfusion; the protection may be related, at least in part, to its ability to reduce lipid peroxidation.

DNA typing for HLA-A and HLA-B identifies disparities between patients and unrelated donors matched by HLA-A and HLA-B serology and HLA-DRB1

High incidences of graft failure and graft-versus-host disease in the recipients of bone marrow transplantations (BMT) from unrelated donors (URD) may reflect the existence of allelic disparities between the patient and the URD despite apparent HLA identity at HLA-A, HLA-B, and HLA-DRB1 loci. To identify the extent and pattern of allelic disparities at HLA-A and HLA-B loci, 128 patients and 484 potential URD were evaluated by DNA typing. DNA typing for HLA-A, HLA-B, and HLA-DRB1 was performed at Memorial Sloan Kettering Cancer Center. HLA-A and HLA-B serotyping on URD was provided by the registries. By original typing (serology for HLA-A and HLA-B; DNA typing for DRB1) 187, 164, and 133 URD were 6/6, 5/6, and 4/6 matches, respectively. Following DNA typing, however, only 52.9% of the originally 6/6 matched URD remained 6/6, while 38.5%, 7.5%, and 1.1% were found to be 5/6, 4/6, and 3/6 matches. The level of disparity was higher in the originally 5/6 (P <.01) and 4/6 (P <.01) matched URD. A higher level of disparity was seen for HLA-B as compared to HLA-A. In addition, a serotype related variation was also noticed. For example, 24.1% of HLA-A2 and 60.1% of HLA-B35 seromatched URD were genotypically disparate, but no disparities were seen for HLA-A1 and HLA-B8. A higher percentage of HLA-A (67. 4%) compared with HLA-B (35.4%) serologic homozygous URD remained genotypically homozygous (P =.01). The level of allelic disparity was lower (P <.01 for 6/6; P =.02 for 5/6) if the patient had one of the 15 most common haplotypes (A1B8DR3, A2B7DR15, A3B7DR15, etc) in comparison to the rest of the group. Outcome studies will answer the question whether these disparities are associated with a higher rate of immunological complications seen with URD-BMT.

[Effect of nitric oxide on the myoelectric activity of sphincter of Oddi and arterial blood pressure of rabbit]

Thirty-two rabbits were used to investigate the effect of nitric oxide (NO) on the myoelectric activity of the sphincter of Oddi (SO) and arterial blood pressure. Intravenous infusion of NG-nitro-L-arginine (L-NNA), an inhibitor of nitric oxide synthase (NOS), caused increase in SO phasic wave amplitude and arterial blood pressure. The increase in SO phasic wave amplitude by infusion of L-NNA was reversed by L-arginine, but arterial blood pressure remained at a high level. It was observed that SO phasic wave amplitude, frequency and arterial blood pressure were significantly decreased by intravenously infusion of sodium nitroprusside (SNP), a substance producing NO. These observations suggest that (1) NO inhibits the resting activity of SO and modulates relaxation of vascular smooth muscle; (2) different tissues show different responses to L-NNA and L-arginine.

Effect of rebamipide on the glycosaminoglycan content of the ulcerated rat stomach

To elucidate the mechanism of the anti-ulcer effect of rebamipide (2-(4-chlorobenzoylamino)-3-[2-(1H)-quinolinon-4-yl] propionic acid), changes in glycosaminoglycan (GAG), uronic acid and hexosamine contents of stomach tissue were examined in rats treated with the ulcer-inducing agents and/or rebamipide. Uronic acid and hexosamine contents in acid hydrolysates of stomach tissue were increased after diethyldithiocarbamate (DDC, 800 mg/kg, s.c.) or histamine (300 mg/kg, i.p.) treatment, and similar changes in the GAG, uronic acid, and hexosamine levels were observed in stomach tissue extracts. Pretreatment with rebamipide (60 mg/kg, i.p.) resulted in an additional increase in the contents of the above components after DDC or histamine treatment. However, rebamipide treatment alone did not increase the gastric contents of GAG and GAG components in normal rats. Gel filtration chromatography of extracted GAGs suggested that DDC, histamine and rebamipide treatments do not cause a change in the aggregated forms of gastric GAGs. These results suggest that rebamipide stimulates the GAG synthesis in the ulcerated stomach and that this effect may contribute to the healing process of gastric ulcer.

Purification of active Na+-K+-ATPase using a new ouabain-affinity column

Ouabain, a specific inhibitor of Na+-K+-ATPase, was coupled to epoxy agarose via a 13-atom spacer to make an affinity column that specifically binds Na+-K+-ATPase. Na+-K+-ATPase from rat and dog kidney was bound to the column and was eluted as a function of enzyme conformation, altered by adding specific combinations of ligands. Na+-K+-ATPase from both sources bound to the column in the presence of Na + ATP + Mg and in solutions containing 30 mM K. No binding was observed in the presence of Na or Na + ATP. These experiments suggest that Na+-K+-ATPase binds to the column under the same conditions that it binds to untethered ouabain. Na+-K+-ATPase already bound to the column was competitively eluted with excess free Na + ouabain or with Na + ATP. The latter eluted active enzyme. For comparable amounts of bound Na+-K+-ATPase, Na + ouabain and Na + ATP eluted more rat than dog Na+-K+-ATPase, consistent with the lower affinity of the rat Na+-K+-ATPase for ouabain. The ouabain-affinity column was used to purify active Na+-K+-ATPase from rat kidney microsomes and rat adrenal glomerulosa cells. The specific activity of the kidney enzyme was increased from approximately 2 to 15 micromol Pi . mg-1 . min-1. Na+-K+-ATPase purified from glomerulosa cells that were prelabeled with [32P]orthophosphate was phosphorylated on the alpha-subunit, suggesting that these cells contain a kinase that phosphorylates Na+-K+-ATPase.

Expression of the basic fibroblast growth factor gene in mild and more severe head injury in the rat

OBJECT

The goal of this study was to investigate the relationship between basic fibroblast growth factor (bFGF) gene expression and neuropathological changes in the hippocampus after varying degrees of brain injury.

METHODS

Mild and severe brain injury in rats was produced by using Marmarou's method. There were 25 animals in each brain injury group and 25 additional animals served as controls. Basic fibroblast growth factor gene expression was investigated by means of RNA hybridization, in situ hybridization, immunohistochemical analysis, and histological analysis using hematoxylin and eosin staining. A 3.7-kb bFGF messenger (m)RNA was detected in the rat hippocampus in both control and injured rats. In the mild injury group its expression was increased at 12 hours after injury and peaked on the 3rd day. Neuronal degeneration in the hippocampal CA2 and CA3 sectors was maximum on that day. In the severe injury group, the expression of the bFGF gene was the same as that in the mild injury group at corresponding times, but the number of surviving neurons in the CA2 and CA3 sectors was much lower than in the mild injury group. In situ hybridization showed that the main cells that expressed bFGF mRNA were pyramidal and granulocytic neurons in all three experimental groups. The number of neurons expressing bFGF mRNA in the severe injury group was less than that in the mild injury group, but the intensity of expression was greater. Immunohistochemical staining showed that the number of neurons expressing the bFGF protein was less in the severe injury group than in the mild injury group.

CONCLUSIONS

It is concluded that after mild injury there is a close relationship between the expression of the bFGF gene and the degree of histological change in the hippocampus; this indicates that as one of the growth factors, bFGF may participate in the protection and repair processes of neurons following brain injury. In severe injury there is a reduced expression of bFGF. The reason for this appears to be that more of the cells that have the potential to express bFGF have died, reducing the ability to express the bFGF gene. Conversely, it is possible that there may be an intrinsic insufficiency of expression of the gene, compatible with the known vulnerability of the hippocampus to many pathological conditions. Consideration should be given to supplying exogenous bFGF to protect the brain, particularly the hippocampus, after injury.

Molecular cloning, expression in Escherichia coli, and characterization of a novel L-3-hydroxyacyl coenzyme A dehydrogenase from pig liver

A novel L-3-hydroxyacyl-CoA dehydrogenase from pig liver has been cloned, expressed, purified, and characterized. This enzyme is a homodimer with a molecular mass of 65.6 kDa, and is distinguished from the dehydrogenase of pig heart by its structural features and catalytic properties. Its subunit, consisting of 302 amino acid residues, has two additional residues in a key region of the active center while it lacks a sequence of seven residues in the NAD+-binding domain, when compared with the subunit of pig heart enzyme. In addition, there are substitutions of four single residues. The catalytic efficiency of pig liver dehydrogenase was significantly greater than that of the heart enzyme for short-chain substrate, but its catalytic rates declined with an increase in substrate chain-lengths. The distinction between pig liver and heart dehydrogenases cannot be attributed to a species difference, and thus it is concluded that there exist different isoforms of monofunctional L-3-hydroxyacyl-CoA dehydrogenases in pig. High level expression of mitochondrial L-3-hydroxyacyl-CoA dehydrogenase in Escherichia coli has provided a very convenient way to purify this important beta-oxidation enzyme. There is substantial homology between pig liver dehydrogenase and various multifunctional beta-oxidation enzymes in the active center of these enzymes; a consensus sequence, HX3PX1-3MXLXE, is proposed as the signature sequence of l-3-hydroxyacyl-CoA dehydrogenases.

A human brain L-3-hydroxyacyl-coenzyme A dehydrogenase is identical to an amyloid beta-peptide-binding protein involved in Alzheimer's disease

A novel L-3-hydroxyacyl-CoA dehydrogenase from human brain has been cloned, expressed, purified, and characterized. This enzyme is a homotetramer with a molecular mass of 108 kDa. Its subunit consists of 261 amino acid residues and has structural features characteristic of short chain dehydrogenases. It was found that the amino acid sequence of this human brain enzyme is identical to that of an endoplasmic reticulum amyloid beta-peptide-binding protein (ERAB), which mediates neurotoxicity in Alzheimer's disease (Yan, S. D., Fu, J., Soto, C., Chen, X., Zhu, H., Al-Mohanna, F., Collison, K., Zhu, A., Stern, E., Saido, T., Tohyama, M., Ogawa, S., Roher, A., and Stern, D. (1997) Nature 389, 689-695). The purification of human brain short chain L-3-hydroxyacyl-CoA dehydrogenase made it possible to characterize the structural and catalytic properties of ERAB. This NAD+-dependent dehydrogenase catalyzes the reversible oxidation of L-3-hydroxyacyl-CoAs to form 3-ketoacyl-CoAs, but it does not act on the D-isomers. The catalytic rate constant of the purified enzyme was estimated to be 37 s-1 with apparent Km values of 89 and 20 microM for acetoacetyl-CoA and NADH, respectively. The activity ratio of this enzyme for substrates with chain lengths of C4, C8, and C16 was approximately 1:2:2. The human short chain L-3-hydroxyacyl-CoA dehydrogenase gene is organized into six exons and five introns and maps to chromosome Xp11.2. The amino-terminal NAD-binding region of the dehydrogenase is encoded by the first three exons, whereas the other exons code for the carboxyl-terminal substrate-binding region harboring putative catalytic residues. The results of this study lead to the conclusion that ERAB involved in neuronal dysfunction is encoded by the human short chain L-3-hydroxyacyl-CoA dehydrogenase gene.

Locus-specific conservation of the HLA class I introns by intra-locus homogenization

The protein-coding sequences of the major histocompatibility complex (MHC) genes are characterized by extraordinarily high polymorphism, apparently maintained by balancing selection, which favors diversity in the peptide-binding domains of the MHC glycoproteins. Here we report that the introns flanking the polymorphic exons of the human MHC class I loci HLA-A, -B, and -C genes have been relatively conserved and have become locus-specific apparently as a result of recombination and subsequent genetic drift, leading to homogenization within loci over evolutionary time. Thus, HLA class I genes have been shaped by contrasting evolutionary forces maintaining polymorphism in the exons and leading to conservation in the introns. This study provides the first extensive analysis of the introns of a highly polymorphic gene family.

Glutamate-119 of the large alpha-subunit is the catalytic base in the hydration of 2-trans-enoyl-coenzyme A catalyzed by the multienzyme complex of fatty acid oxidation from Escherichia coli

Glu139 of the large alpha-subunit of the multienzyme complex of fatty acid oxidation from Escherichia coli was identified as the catalytic residue of enoyl-CoA hydratase [Yang, S.-Y., He, X.-Y., & Schulz, H. (1995) Biochemistry 34, 6441-6447]. To determine whether any of the other conserved protic residues is directly involved in the hydratase catalysis, the multienzyme complexes with either an alpha/Asp69 --> Asn or an alpha/Glu119 --> Gln mutation were overproduced and characterized. The catalytic properties of 3-ketoacyl-CoA thiolase and l-3-hydroxyacyl-CoA dehydrogenase of the mutant complexes were almost unaffected. The amidation of Asp69 and Glu119 caused a 7.6- and 88-fold decrease, respectively, in the kcat of enoyl-CoA hydratase without a significant change in the Km value of the hydratase as well as a 5.9- and 62-fold increase, respectively, in the Km of Delta3-cis-Delta2-trans-enoyl-CoA isomerase with a very small decrease in the kcat of the latter enzyme. The data suggest that the carboxyl group of Glu119 is particularly important to the catalytic activity of enoyl-CoA hydratase. Furthermore, the wild-type hydratase shows a bell-shaped pH dependence of the kcat/Km with pKa values of 5.9 and 9.2, whereas the Glu119 --> Gln mutant hydratase has only a single pKa of 9.5. A simple explanation for these observations is that a deprotonated Glu119 and a protonated Glu139 are required for the high kcat of the enoyl-CoA hydratase. The results of site-directed mutagenesis studies, together with the structural information about the spatial arrangement of two conserved glutamate residues of rat liver enoyl-CoA hydratase [Engel, C. K., Mathieu, M., Zeelen, J. P., Hiltunen, J. K., and Wierenga, R. K. (1996) EMBO J. 15, 5135-5145] to which Glu119 and Glu139 of the large alpha-subunit correspond, lead to the conclusion that the gamma-carboxyl group of Glu119 serves as the second general acid-base functional group in catalyzing the hydration of 2-trans-enoyl-CoA.

Cloning and expression of the fadH gene and characterization of the gene product 2,4-dienoyl coenzyme A reductase from Escherichia coli

The fadH gene coding for an NADPH-dependent 2.4-dienoyl-CoA reductase from Escherichia coli has been cloned by the polymerase chain reaction. This gene is located at 67.65 min on the E. coli chromosome. The complete open reading frame contains 2019 bp coding for the processed protein of 671 amino acid residues, with a calculated molecular mass of 72.55 kDa, which lacks the N-terminal methionine. Construction and expression of the plasmid pNDH, which contained the fadH gene under the control of the T7 promoter, resulted in a 110-fold increase in the reductase activity above the level detected in E. coli cells containing the control vector. The kinetic parameters of the purified reductase were determined to be 50 microM and 2.3 microM for the Km values of NADPH and 2-trans, 4-trans-decadienoyl-CoA, respectively, and 16 s(-1) for the k(cat) value. Analysis of the kinetic data revealed that the reaction catalyzed by this enzyme proceeds via a ping-pong mechanism. The observed dissimilarity between the E. coli and mammalian 2,4-dienoyl-CoA reductase sequences suggests that they have evolved from distinct ancestral genes. Sequence analysis also suggests that the N-terminal part of the E. coli reductase contains the FAD-binding domain whereas the NADPH-binding domain is located in the C-terminal region of the protein.

Dimorphic primers derived from intron 1 for use in the molecular typing of HLA-B alleles

We have identified a dimorphic site in intron 1 of the HLA-B gene. Oligotyping was performed on about 3000 samples using primers derived from this dimorphic site in combination with a locus-specific primer derived from intron 3. The distribution of B-alleles bearing each of the dimorphic sequences was approximately equal. These primers were mutually exclusive and yielded approximately 50% of the heterozygous samples as apparently homozygous in PCR products. Intermediate and almost high-resolution oligotyping of HLA-B alleles was achieved using 35 and 63 hybridization probes, respectively. This dimorphic site will provide a useful tool for other PCR-based HLA-B typing approaches.

The pentanucleotide ATTGG, the "inverted CCAAT," is an essential element for HLA class I gene transcription

The HLA class I genes, HLA-A, -B, and -C, contain an inverted CCAAT sequence (ATTGG) located 20 bp upstream of the canonical CCAAT and approximately 70 bp upstream of the transcription initiation site. We have investigated the transcriptional function of the class I inverted CCAAT sequence using the HLA-normal cell line, HeLa. Deletion, mutation, or inversion of the inverted CCAAT sequence abrogated or reduced the activity of the class I promoter, as assessed by luciferase reporter gene assays in transient gene expression experiments. This activity coincided with occupancy of the inverted CCAAT motif, as tested by electrophoretic mobility shift assays using the wild-type sequence and mutated variants of the sequence. The ATTGG-binding protein was not CP2, NF-1, or other known CCAAT-binding proteins, but the complex may contain a CP1/NF-Y-like protein. Our results indicate that this inverted CCAAT sequence is an essential element for the expression of HLA class I genes and that its transcriptional activity depends upon the sequence, position, and orientation of the pentanucleotide.

The pentanucleotide ATTGG, the "inverted CCAAT," is an essential element for HLA class I gene transcription

The HLA class I genes, HLA-A, -B, and -C, contain an inverted CCAAT sequence (ATTGG) located 20 bp upstream of the canonical CCAAT and approximately 70 bp upstream of the transcription initiation site. We have investigated the transcriptional function of the class I inverted CCAAT sequence using the HLA-normal cell line, HeLa. Deletion, mutation, or inversion of the inverted CCAAT sequence abrogated or reduced the activity of the class I promoter, as assessed by luciferase reporter gene assays in transient gene expression experiments. This activity coincided with occupancy of the inverted CCAAT motif, as tested by electrophoretic mobility shift assays using the wild-type sequence and mutated variants of the sequence. The ATTGG-binding protein was not CP2, NF-1, or other known CCAAT-binding proteins, but the complex may contain a CP1/NF-Y-like protein. Our results indicate that this inverted CCAAT sequence is an essential element for the expression of HLA class I genes and that its transcriptional activity depends upon the sequence, position, and orientation of the pentanucleotide.